- Prediabetes is an intermediate state of hyperglycaemia, where blood glucose levels are elevated but not high enough to meet the criteria for type 2 diabetes (T2DM).
- It is a reversible condition with significant potential to progress to diabetes if not addressed.
- Prediabetes is associated with an increased risk of cardiovascular disease and can be effectively managed with lifestyle interventions.
- Early detection and intervention are essential to prevent progression to type 2 diabetes and associated complications
- Without intervention, up to 70% of individuals with prediabetes will eventually develop type 2 diabetes.
1. Definition
- Prediabetes is defined as an intermediate metabolic state where blood glucose levels are higher than normal but do not meet the threshold for a diabetes diagnosis
- It is an early warning sign for type 2 diabetes, as individuals with prediabetes are at higher risk of developing the condition.
2. Epidemiology
- Prevalence: In the UK, prediabetes affects around 7 million adults, equating to 10-15% of the population. This number is rising due to increasing obesity rates and sedentary lifestyles.
- Age: Prediabetes is more common in individuals over the age of 40, but younger adults and adolescents are increasingly affected, particularly those with obesity.
- Gender and ethnicity: It is slightly more common in men, and certain ethnic groups, particularly South Asian, African-Caribbean, and Middle Eastern populations, are at higher risk.
3. Risk factors
- Obesity, particularly central obesity (high waist circumference)
- Sedentary lifestyle with minimal physical activity
- Family history of type 2 diabetes or prediabetes
- Age over 40 years (or over 25 in high-risk ethnic groups)
- Ethnicity: South Asian, African-Caribbean, and Middle Eastern descent are at higher risk
- History of gestational diabetes or having given birth to a baby weighing >4kg
- Polycystic ovary syndrome (PCOS)
- Hypertension and dyslipidaemia (low HDL cholesterol and/or high triglycerides).
4. Causes
The primary cause of prediabetes is insulin resistance. In this state, the body’s cells become less responsive to insulin, resulting in impaired glucose uptake and higher circulating blood sugar levels. Contributing factors include:
- Genetics: A family history of diabetes predisposes individuals to prediabetes
- Excess body fat: Particularly visceral fat, which interferes with insulin signalling
- Poor diet: High intake of refined carbohydrates and sugars, along with a lack of fibre, leads to glucose dysregulation
- Physical inactivity: A sedentary lifestyle reduces insulin sensitivity, exacerbating the problem.
5. Symptoms
Prediabetes is often asymptomatic, which is a. the problem, and b. why it is frequently detected through routine screening. However, some individuals may experience vague or mild symptoms, such as:
- Fatigue: A result of inefficient glucose utilisation
- Increased thirst (polydipsia) or frequent urination (polyuria), although less common than in diabetes
- Blurry vision: Due to fluctuating blood sugar levels.
These symptoms are typically mild and are more characteristic of early type 2 diabetes than prediabetes itself.
6. Diagnosis
Prediabetes is diagnosed based on blood glucose and HbA1C measurements:
Glucose
- Normal human blood glucose = 4-6 mmol/L
- Diabetes is diagnosed if random blood glucose > 11 mmol/L
- Prediabetes is diagnosed if random blood glucose = 7-11 mmol/L.
HbA1C
The haemoglobin A1C test (HbA1C) measures average blood glucose level over previous 2-3 months. This test doesn’t require fasting and can be done any time.
- Normal HbA1c = 20-41 mmol/mol (or 4-6%)
- Prediabetes is diagnosed if HbA1c = 42-47 mmol/L (6-6.5%)
- Diabetes is diagnosed if HbA1c = 48 mmol/mol or over (>6.5%).
Note 1. An HbA1C value of 42-47 mmol/mol is diagnostic for prediabetes. The higher the A1C, the higher the risk that your prediabetes will progress to type 2 diabetes.
Note 2. Ideally glucose and HbA1C should be measured twice at the start, to confirm the diagnosis.
Investigation
- Fasting blood glucose: The key test for identifying a raised fasting glucose
- Oral glucose tolerance test (OGTT): A 2-hour glucose measurement after consuming 75g of glucose; useful for diagnosing impaired glucose tolerance
- HbA1c: Reflects average blood glucose levels over the past 2-3 months and is commonly used for both screening and monitoring
- Lipid profile: Checking for dyslipidaemia (elevated triglycerides, low HDL cholesterol), which often coexists with prediabetes
- Blood pressure measurement: Hypertension is commonly associated with insulin resistance and should be assessed.
Differential diagnosis
The primary condition that prediabetes must be differentiated from is type 2 diabetes. However, other conditions that can mimic hyperglycaemia should also be considered:
- Type 1 diabetes: Although less common, autoimmune diabetes can present with mild hyperglycaemia in the early stages (latent autoimmune diabetes in adults – LADA)
- Maturity-onset diabetes of the young (MODY): A genetic form of diabetes that can present in young adults
- Cushing’s syndrome: Hyperglycaemia can occur due to excessive cortisol production
- Hyperthyroidism: Can contribute to elevated blood sugar levels.
7. Treatment
The management of prediabetes focuses on lifestyle modifications to reverse the condition and reduce the risk of progression to type 2 diabetes:
- Lifestyle interventions
- Weight loss: A 5-10% reduction in body weight can significantly improve insulin sensitivity and reduce the risk of developing type 2 diabetes
- Dietary changes: Encouraging a diet rich in whole grains, fruits, vegetables, lean protein, and healthy fats. Reducing refined sugars and processed foods is crucial
- Physical activity: At least 150 minutes of moderate-intensity exercise per week is recommended Regular physical activity improves insulin sensitivity and aids weight management.
- Pharmacotherapy
- Metformin: Can be considered in high-risk individuals, particularly those with a BMI ≥35, who are under 60 years old, or women with a history of gestational diabetes
- Glucose-lowering agents (e.g., GLP-1 receptor agonists or SGLT2 inhibitors) may be considered in select cases, although not routinely used for prediabetes.
- Monitoring
Is prediabetes reversible?
Yes. If you have prediabetes, losing weight if you are overweight, and getting regular physical activity, can: (1) reverse it, or at least (2) significantly lower your risk of developing type 2 diabetes. It can even go away completely, so you do not have diabetes or prediabetes.
8. Complications
If untreated, prediabetes can lead to several serious complications:
- Progression to type 2 diabetes: Approximately 5-10% of individuals with prediabetes develop type 2 diabetes annually.
- Cardiovascular disease (CVD): Prediabetes is independently associated with an increased risk of cardiovascular events, including myocardial infarction and stroke.
- Microvascular complications: While rare in prediabetes, prolonged hyperglycaemia can lead to early signs of neuropathy, nephropathy, or retinopathy.
9. Prognosis
- The prognosis of prediabetes is variable and depends heavily on lifestyle changes
- Without intervention, up to 70% of individuals with prediabetes will eventually develop type 2 diabetes
- However, with effective lifestyle modification, the risk of progression can be reduced by 40-70%. Early intervention can also reduce the risk of cardiovascular disease and other metabolic complications.
Long-term follow-up of prediabetes
If you have (or have had) prediabetes, you need your blood glucose monitoring for the rest of your life – every three months.
10. Prevention
Preventing prediabetes involves addressing modifiable risk factors through public health measures and individual strategies:
- Healthy lifestyle promotion:
- Diet: Public health initiatives promoting healthy eating and reducing sugar intake can help prevent prediabetes.
- Exercise: Regular physical activity should be encouraged from an early age, particularly in children and adolescents at higher risk.
- Public health interventions:
- Campaigns to reduce obesity, improve access to healthier food options, and increase opportunities for physical activity are essential.
- Screening and early detection:
- Routine screening in high-risk individuals (e.g., those over 40, with obesity, or from high-risk ethnic groups) is crucial to identify prediabetes early.
